IPv6 link local addresses and device discovery

From https://astrid.tech/2024/05/28/0/ping-ff02-1/

With IPv6 enabled on a device, you can find their IP via ping (even without DHCP lease) - e.g if the connected Ethernet device is enp4s0:

% ping ff02::1%enp4s0
PING ff02::1%enp4s0(ff02::1%enp4s0) 56 data bytes
64 bytes from fe80::54a4:74f4:3735:33ad%enp4s0: icmp_seq=1 ttl=64 time=0.023 ms
64 bytes from fe80::da9d:67ff:fe26:463f%enp4s0: icmp_seq=1 ttl=64 time=0.243 ms
64 bytes from fe80::28c7:cb09:9bf6:1062%enp4s0: icmp_seq=1 ttl=64 time=0.293 ms
64 bytes from fe80::a02:8eff:fe9e:cf67%enp4s0: icmp_seq=1 ttl=64 time=0.796 ms
64 bytes from fe80::5054:ff:fed6:96c%enp4s0: icmp_seq=1 ttl=64 time=0.888 ms
64 bytes from fe80::768e:f8ff:feed:b700%enp4s0: icmp_seq=1 ttl=64 time=3.45 ms
^C
--- ff02::1%enp4s0 ping statistics ---
1 packets transmitted, 1 received, +5 duplicates, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.023/0.949/3.453/1.160 ms

This works even if the device hasn't DHCP'd.

If the network DHCP server isn't assigning all devices IPv6 addresses, it can be a bit tedious to identify which device is which, but still potentially useful